Common antibiotics taken during pregnancy could be linked to an increase in birth defects

Women taking common antibiotics during the first trimester of their pregnancy are at greater risk of seeing their child born with birth defects, according to new research.

The study, published on Wednesday (19 Feb) in the medical journal BMJ, found an increased risk of birth defects in the children of women who were prescribed macrolides during the first three months of pregnancy, compared to mothers who were prescribed penicillin.

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What are macrolide antibiotics?

Macrolide antibiotics are used to treat infections such as pneumonia and bronchitis, as well as urinary and skin conditions, plus sexually transmitted diseases. They are usually prescribed to patients who are allergic to penicillin.

According to the study, macrolides are one of the most frequently prescribed antibiotics in western countries.

Increased risk of heart problems

Scientists from University College London analysed data from 104,605 children born in the United Kingdom between 1990 and 2016, who were born to mothers prescribed either penicillin or macrolides.

The team found that giving macrolides to pregnant women during the first trimester increased the risk of major malformations in 28 of 1,000 births, compared to 18 per 1,000 births with penicillin. Specifically, the risk of the baby being born with heart problems was higher.

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The study also revealed that taking macrolides during any trimester was associated with an increased risk of genital malformations.

The study did not find a link between macrolides prescription and neurodevelopmental disorders. There was also no associated risk between birth defects and macrolides prescribed before conception.

Alternative antibiotics

University College London Professor Ruth Gilbert, one of the authors of the study, said this is a small but still significant increase and, based on these findings, pregnant women and their doctors should find an alternative, depending on the type of infection.

Gilbert also warned about the risks of not taking antibiotics at all.

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“If you’ve got a bacterial infection, it’s really important to take antibiotics because infection itself can be really damaging to the unborn baby,” she said.

The study is based on a series of analyses of a broad health database of general practitioners in the UK. Gilbert said an even larger data set could provide insight on less common birth defects and other outcomes from taking certain antibiotics.

The team concluded that macrolides should be taken with “caution” during pregnancy and, if possible, alternative antibiotics should be prescribed until further research is available.

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